text: It is resistant to high temp. and corrosion, and has high separating property and low resistance. Its film, on the external or internal surface, has a hole gradient highly selective to gas and catalytic-separable support. It is made with alumina, silicon dioxide or titania as the main material added with clay and feldspar. After processing, moulding, drying and loading in furnace, it is baked at a temperature of 1100-1550 degrees C. The ceramic film has hole operture 0.1-15 mu m, porosity 30-55%, thickness 1-200 mu m, in 2-10 layers. The tubular ceramic with hole gradient has a diameter of 4-40 mm, length 25-1500 mm and thickness of 3-10 mm.